Throttle return systems for carburettors

ABSTRACT

The shaft of a carburettor throttle is provided with a first return torsion spring one end of which abuts a lug of the carburettor body. A second return spring is stressed between the lug and the stationary end of the first spring. If the first spring fails, the second spring may exert a return force on the throttle which is almost as high as that of the first spring.

United States Patent ['91 Mennesson THROTTLE RETURN SYSTEMS FORCARBURETIORS Francois Mennesson, N anterre, France Societe Industriellede Brevets et dEttrdes S.I.B.E., Neuilly-sur-Seine, France Filed: Mar.26, 1974 Appl. No.: 454,834

Inventor:

[73] Assignee:

Foreign pp ication Priority Date p 3 Franee 73.!2369 U18, Chm... 123/198D; 123/198 DB; 125/142; 74/513: 180/82 In c l' iiliilll i!llull II I[58] Field 123/198 D, [98 DB, 142, 123/198 R; 74489.2, 96, 513; 180/82,82.1

Retereneee Cited UNITED STATES PATENTS 3326.919 12/19' MaeMillen l23/l98D8 1 Dec. 23, 1975 3.698.372 10/1972 Eshelman et alt 123/198 D X3,699,943 10/1972 Eshelman 123/198 DB 3,704,635 lZ/I972 Eshelman 123/195D X 3,760,786 9/1973 Mlrlh 180/82 R Primary Examiner-Charles J. MyhreAssistant Examiner-Ira S. Lazarus Attorney. Agent. or Firm-Stevens.Davis, Miller & Mother 2 Ciaims, 4 Drawing Figures U.S. Patent Dec. 23,1975 Sheet 1 of2 3,927,657

U.S. Patent Dec. 23, 1975 Sheet 2 of2 3,927,657

THROTTLE RETURN SYSTEMS FOR CARBURETTORS BACKGROUND AND SUMMARY OF THEINVENTION The invention relates to internal combustion enginecarburettors of the kind which comprise, in an intake manifold, athrottling member carried by a rotary shaft and connected to anaccelerator control which enables the driver to open such member againstthe force of resilient return means which act on such shaft and tend toreturn the throttling member into a minimum opening positioncorresponding to engine idling.

Such resilient return means have been formed by a single spring which issubjected to a deforming force when the driver opens the throttlingmember. Safety requirements now lay down that at least two separatereturn springs must be provided each of which is able to return thethrottling member to its idling position. The simplest method wouldconsist in disposing the two springs in parallel, but this would resultin practice in doubling the force which the driver must exert to openthe throttling member, since each spring must exert force adequate toenable it to reclose the throttling member on its own i.e., if the otherspring breaks.

It is an object of the invention to provide such return means using twosprings without however appreciably increasing the force required toopen the throttling member and without substantially increasing thecomplexity of the construction.

For this purpose, there is provided, in a carburettor for internalcombustion engine having a throttle member secured to a rotary shaft andadapted to be angularly moved with respect to the carburettor body bycontrol means, resilient return means for biasing said throttle membertoward a minimum opening position, comprising: a first torsional returnspring having a first end retained in fixed relation with respect to thecarburettor body and its other end operatively connected to said shaftfor exerting a return force on said shaft; a second torsion springhaving a first end which is retained in fixed relation with respect tothe carburettor body and its other end in abutting relation against saidfirst end of the first spring which retains said first spring instressed condition; and abutting means nonrotatably connected to saidthrottling member and located on the path followed by said other end ofthe second spring when clear from abutment against the first spring.

Under normal operating conditions only the first spring exerts a returnforce. If the first spring fails, the second end of the second springloses its bearing and starts to co-operate with the abutting meansconnected to the throttle member shaft to exert a return force on thethrottle member.

In a particular embodiment, the two torsion springs are coil springswound on the throttling member shaft each on one side of a lever securedto the shaft and bearing two pins substantially parallel with the shaftand turned towards the two springs respectively, and the carburettorbody has a projecting lug acting as a stop for the first ends of the twosprings; one of the pins normally acts as a bearing for the second endof the first spring; the other pin constitutes the said abutting meansnon-rotatably connected to the throttling member shaft.

The invention will be better understood from the following descriptionwith reference to the accompanying drawings, such description anddrawings relating to a preferred embodiment.

SHORT DESCRIPTION OF THE DRAWINGS FIGS. 1 and 2 show, sectioned alongthe line Il in FIG. 2 and the line II-Il in FIG. 1 respectively, thelower part of a carburettor whose throttling member is completelyopened.

FIG. 3, similar to FIG. 2, shows the same carburettor with itsthrottling member in its minimum opening position.

FIG. 4 shows, similarly to FIG. 3 but with a slight offsetting of thesectional plane, the same carburettor in which only the second torsionspring is in operation.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring to FIGS. 1-4, there isshown the body 1 of a carburettor of downdraught type whose conventionalelements are not illustrated. An inlet manifold 2 extends through thebody and contains a throttling member or butterfly 3 secured to a rotaryshaft 4 by screws 5. One of the ends of the shaft 4 is screw-threaded toreceive a nut 6 which retains a lever 7 which is connected to anaccelerator control (not shown).

A lever 8 connected to the shaft 4 bears a pin 9 parallel therewithwhich acts as a bearing for one end 16 of a first helical torsion spring10. The other end I5 of the spring 10 bears against a projecting lug llintegral with the carburettor body 1. When the butterfly 3 is opened(counterclockwise, from the position illustrated in FIG. 3 to thatillustrated in FIG. 2), the resulting movement of the pin 9 winds thespring 10 around the shaft 4, so that the spring biases the butterflytowards its closed position.

The construction described until now is conventional. The shaft 4carries a second helical torsion spring 12 one end 13 of which bearsagainst the lug II, the other end portion 14 being bent (as appears onFIG. 1) so that it normally bears against the end portion 15 of thespring 10. The lever 8 carries a second pin 17 disposed on the path ofthe end I4 of the spring 12 when the end portion 14 is not retained bythe end portion 15 of the first spring 10.

In the particular embodiment illustrated, the springs 10 and 12 aredisposed each on one side of the lever B, the spring 10 being closest tothe frame I. The pin 9 projects towards the body I and the pin 17 in theopposite direction. The end portions I3, 14 (before its bend), l5 and 16are directed tangentially with respect to the helical portion of thesprings l0, 12. The bend of the end portion 14 is located level with thelever 8 (FIG. I).

The return means operate as follows. During idling (FIG. 3), undernormal conditions, the spring 10 alone exerts a closure torque on theshaft 4 of the butterfly 3 via its end portion 16, the pin 9 and thelever 8. The spring 12 does not act on the shaft 4, since its two endsI3, 14 are retained by stationary parts. The torsion force of the spring12 is so selected that the force exerted by its end portion 14 on theend portion I5 of the spring 10 does not move the end I5 clear ofabutment against the lug 11. If the butterfly 3 is opened (i.e., movedtoward the angular position illustrated in FIGS. 1 and 2), the force tobe overcome is therefore only that of the spring I0.

lffor any reason the spring 10 is broken (as shown on FIG. 4, on whichthe spring I0 has been omitted), the end I4 of the spring 12 is releasedand moves into abutment with the pin 17 of the lever 8, thereby exertinga closure torque on the butterfly 3. If the throttle is then opened, theforce to be overcome is only that of the spring 12.

Conversely, if the spring 12 gets broken, the spring continues tooperate as described hereinbefore.

As a result, there is obtained a simple return system having twoseparate springs whose forces are exerted separately and notsimultaneously, so that the force needed to open the butterfly is notappreciably increased.

I claim:

1. In a carburettor for an internal combustion engine having a throttlemember secured to a rotary shaft and adapted to be angularly moved withrespect to the carburrettor body by control means, resilient returnmeans for biasing said throttle member toward a minimum openingposition, comprising: a first helical torsion return spring wound aroundthe shaft and having a first end retained in fixed relation with respectto the carburettor body and its other end operatively connected to saidshaft for exerting a return force on said shaft; a second helicaltorsion spring wound around the shaft and having a first end which isretained in fixed relation with respect to the carburettor body and itsother end in abutting relation against said first end of the firstspring which retains said second spring in stressed condition; a lever;and abutting means carried by said lcver, said abutting means beingnon-rotatably connected to said throttle member and located on the pathfollowed by said other end of the second spring when clear fromabutment, whereby said second spring unwinds upon breakage of said firstspring and exerts on said abutting means a force tending to move saidthrottle member toward its closed condition.

2. A carburettor as set forth in claim I, wherein the two torsionsprings are wound on opposite sides of said lever which carries two pinssubstantially parallel with the shaft and turned towards the two springsrespectively, and the carburettor body has a projecting lug acting as abearing for the first ends of the two springs, one of the pins acting asa bearing for the second end of the first spring, and the other pincomprising said abutting means.

1. In a carburettor for an internal combustion engine having a throttlemember secured to a rotary shaft and adapted to be angularly moved withrespect to the carburrettor body by control means, resilient returnmeans for biasing said throttle member toward a minimum openingposition, comprising: a first helical torsion return spring wound aroundthe shaft and having a first end retained in fixed relation with respectto the carburettor body and its other end operatively connected to saidshaft for exerting a return force on said shaft; a second helicaltorsion spring wound around the shaft and having a first end which isretained in fixed relation with respect to the carburettor body and itsother end in abutting relation against said first end of the firstspring which retains said second spring in stressed condition; a lever;and abutting means carried by said lever, said abutting means beingnon-rotatably connected to said throttle member and located on the pathfollowed by said other end of the second spring when clear fromabutment, whereby said second spring unwinds upon breakage of said firstspring and exerts on said abutting means a force tending to move saidthrottle member toward its closed condition.
 2. A carburettor as setforth in claim 1, wherein the two torsion springs are wound on oppositesides of said lever which carries two pins substantially parallel withthe shaft and turned towards the two springs respectively, and thecarburettor body has a projecting lug acting as a bearing for the firstends of the two springs, one of the pins acting as a bearing for thesecond end of the first spring, and the other pin comprising saidabutting means.